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Frequent Contributor II
Posts: 108
Registered: ‎08-31-2010

roaming between aps

Any one got any pointers on improving the roaming between aps? In my situation it geld like my stations are hanging on a little too long to an AP and maybe they could encourage the station onto a AP that has stronger signal? Any thoughts? Feeling like a leave the defaults alone answer coming on! ;-)
Guru Elite
Posts: 20,773
Registered: ‎03-29-2007

Re: roaming between aps


soapdish wrote:
Any one got any pointers on improving the roaming between aps? In my situation it geld like my stations are hanging on a little too long to an AP and maybe they could encourage the station onto a AP that has stronger signal? Any thoughts? Feeling like a leave the defaults alone answer coming on! ;-)

The wifi client driver software determines when it roams between one device or another.  That logic is usually specfic to the manufacturer of the card or driver software.  The behavior can also change between driver software versions, depending.  It usually uses a range of metrics like signal strength, signal quality, how low the signal has to be when it roams, etc.

 

The local-probe-response-threshold paramater in the SSID profile can change roaming behavior, but it does not completely eliminate individual client behavior.  Clients that are already aggressive become more aggressive and you might not want that, so it is important to determine if the issue is more on the client side, infrastructure side or if you have an issue, at all.

 

Putting access points on two different floors directly over one another instead of staggering them can make a client prefer an access point on the floor above, rather than one that is on the same floor.  The Validated Reference Design on Roaming goes into great detail about all the arguments surounding mobile devices and how to optimize for them.  I would just be cutting and pasting from that document into my answer....

 

The big question is, do you have an issue and it is worth changing the roaming behavior of all your clients for it..

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Frequent Contributor II
Posts: 108
Registered: ‎08-31-2010

Re: roaming between aps

Short answer is no. Thanks
New Contributor
Posts: 4
Registered: ‎09-12-2012

Re: roaming between aps

Depending on a bunch of different factors you can reduce the time the stations hang on by disabling the lower data rates.

 

As a station moves away from an AP, errors increase and signal strength decreases. When the signal strength gets below its configured minimum, it will reduce the data rate. Disabling the lower data rates means that the station cannot go below whatever low-water-mark you set and roams to an AP with a stronger signal.

 

 

Frequent Contributor II
Posts: 118
Registered: ‎02-10-2011

Re: roaming between aps

Where do you disable the lower data rates?

Guru Elite
Posts: 20,773
Registered: ‎03-29-2007

Re: roaming between aps

To be clear, removing lower data rates does NOT help with roaming BUT can present interoperability issues for clients that EXPECT those lower rates to be there.  If you do not control 100% of your clients and cannot do interoperability testing, it can be very troublesome down the road.

 

A thread on how to remove lower rates is here:  http://community.arubanetworks.com/t5/Wireless-and-RF/Can-it-be-turned-off-802-11b/m-p/5338/highlight/true#M114

 

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

New Contributor
Posts: 4
Registered: ‎09-12-2012

Re: roaming between aps

...except that it does. As you mentioned earlier, the client driver uses a number of variables including signal strength to determine whether it should roam. As the signal strength decreases, clients will drop to lower data rates in order to stay above a minimum threshold (usually somewhere around -85.) It will only roam if it has no lower rate to go to and the signal drops below that threshold. Therefore, if you remove the lower rates it has to roam earlier (otherwise, it will drop all the way down to 1M if it can maintain that minimum threshold.)

 

I agree that it can cause interoperability issues for some clients. I would include that in the list of factors that I said it would depend on.

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